our was just running like crap pretty much all of the time. We paid £10 for another carb that was supposedly off a good runner but it didnt make any difference.
We now run on a Nikki carb (straight replacement on the manifold) and it runs like a dream.
From that, it was either 2 carbs that were knackered, or something associated with the emission stuff from the original carb. Dunno which cos we didnt work through the problem